Gyroscope stabilizing mechanism



April 13, 1948. c. 'r DAVENPORT ,4

GYROSCOPE STABILIZING MECHANISM Filed July 27, 1944' JNVENTOR.

049/9455 mum/Pm? Patented Apr. 13 1948 UNITED STATES PATENT OFFICE toArma Corporation, Brooklyn,

ration of New York N. Y., a corpo- Application July 27, 1944, Serial No.546,894

6 Claims. 1

This invention relates to stabilizing mechanism for gyroscopes, and hasparticular reference to self-erecting mechanism for gyro verticals usedon unstable platforms, such as aircraft and ships, although theinvention is not limited to that use.

The friction in the bearings of the gimbal suspension of a gyroscopeinvariably produces sufficient resistance to free movement to cause thegyroscope to precess slowly until the gyro scope points in anunpredictable direction, thus rendering it unreliable as to fixed datumpoint, such as a vertical or zenith indicator. In order to counteractthis effect, connected mercury tank ballistic systems are often used tointroduce an erecting couple ninety degrees from the plane of thedisturbing force. Mercury tank erecting systems are critical and slow inoperation, require special metals and scaling to preclude deteriorationand consequent impairment of the effectiveness of the mercury, and areotherwise generally unsatisfactory. Another gravity erecting systemeliminating some of the objections to mercury tank ballistic systems isthe ball type gravitational systems of which several examples areillustrated in U. S. Patent No. 1,311,768, issued July 29, 1919, to J.and J. G. Gray. However, the balls must be positively driven at aconstant critical low speed difiicult to attain, and subsidiarydisturbing forces are introduced by the balls themselves during extremetilts of the gyroscope, so that such systems frequently cause thegyroscope to indicate a false vertical which is difficult to detect.

In accordance with the present invention, a gravitational erectingsystem for vertical type gyroscopes is provided which eliminates theobjections to prior types and which is extremely simple in constructionand operation, as well as direct and rapid in its function ofintroducing a counter precession to correct all disturbances, to the endthat vertical or zenith indicating gyroscopes embodying the system ofthis invention are true and constant in their indication.

The invention consists in balls rolling in equally-spacedcircularly-arranged grooves, each having a curvature of less radius thanthe radius of rotation of the corresponding balls about the axis of thegyroscope around which they are driven at relatively low speed in anormally horizontal plane. The resulting synchronous scillation of theballs in their respective grooves in response to a disturbance createsan erecting couple at right angles to the disturbing force, whichquickly and accurately rights the gyro- For a more completeunderstanding of the invention, reference may be had to theaccompanyscope without causing excessive coming or over-I shooting ofthe axis about the true vertical.

ing drawings, in which:

Figure l is a simplified perspective view of a vertical or zenithindicating gyroscope fitted with the stabilizing or tilt-correctingsystem of this invention;

Fig. 2 is a plan view of the tilt-correcting element of the system ofFig. 1;

Fig. 3 is a view of the tilt-correcting element show in tilted positionto illustrate its correcting operation, and

Fig. 4 is an axial section through the apparatus of Fig. 1 showing thereduction gear drive of the tilt-correcting element.

Referring to Fig. 1 of the drawings, G designates a gyroscope having anelectrically-driven or air-spun rotor, indicated at 9 in Fig. 4,journaled about a-normally vertical axis within casing It, which ismounted in a Cardan suspension for angular movement about two mutuallyperpendicular axes normally lying in ahorizontal plane, so that thegyroscope has three degrees of freedom. The Cardan suspension of thecasing it includes opposite free bearings H and i2 in the gimbal ringl3, which in turn is supported in opposite free bearings Hi and 15 atright angles to bearings II and I2 and mounted on posts It and Il fixedfirmly on the surface l8 which is the tilting or unstable platform on aship, airplane, or the like. Theoretically, the gyroscope is unafiectedby this suspension, but the friction in the bearings ll, [2, M and I5,although small, is nevertheless sulficient to introduce disturbingforces causing the gyroscope axis to Wander from true vertical. Thepresent invention not only corrects this condition, but provides anefiicient stabilizing system operating by synchronous oscillation ofballs rather than by the simple rolling of balls, as in the prior art.

The stabilizing system of this invention includes a normally horizontaldisc l9 mounted at the bottom of the gyroscope casing it on a shortshaft 20 coincident with the spin axis and driven by the gyroscope rotorthrough conventional reducing gearing housed within extension. ID of thecasing Ill, so that the disc I!) rotates in the same direction but at amuch lower rate of speed than the rotor. The reducing gearing drive ofdisc I9 is shown in Fig. 4 and comprises a pinion 5 on the lower end ofthe shaft of rotor 9, meshing with a large gear 6 Whose connected pinionl meshes with large gear 8 on shaft 20 which supports and rotates discIS.

The disc [9, shown in enlarged plan view in Fig. 2, is provided atregularly spaced intervals, such as 90, with relatively short curved orcrescentshaped grooves 2|, 22, 23 and 2 3, each spaced from the centerof shaft 20 an equal radial distance r, and each having a curvatureequal to R, which is considerably less than the radius r. The length,spacing, radial distance r, and curvature R of the grooves 2 l-2 ldependon the design and requirements of the gyroscope G, and for specialpurposes the grooves may be non-circular, such as elliptical, forexample.

Positioned for rolling movement in grooves 2 i1: 2 are correspondingballs 2528, respectively, each having equal, considerablegmass. Eachball is accordingly free to roll back and forth in its correspondinggroove under the influence of gravity and of centrifugal force also.

During operation of the stabilizing system of this invention, the disci9 is driven at constant relatively low speed Icy supporting shaft 29around the axis of the latter in a normally horiontal plane and,although the disc I9 is thus positively driven, the balls 25-48 are not,being free to roll back and forth in their grooves, as described. Whenthe disc in is horizontal, the balls 25-28 are kept by centrifugal forceat their outermost radial points, which are on the radii passing throughtheir median points as shown. However, as soon as the gyroscopeliltilts, due to some disturbing force, the disc it also tilts and theballs 2528 are subjected to gravity as well as to centrifugal force.Accordingly, the balls begin to change their relative positionsaccording to their location, at any point in their bodily rotation aboutthe center of shaft 29.

The condition occurring upon tilting of the disc 49 to the left is shownin Fig. 3, assuming the planeof the drawing to be horizontal, The disci6 is being rotated in the direction of the arrow 22. An index marl; isshown on the disc at and various angular positions are marked withreference to the mark til, as 90, 180, and 270". At the instantillustrated, the index 33 is at the position 0 which is 90counterclockwise from the lowermost point of the indicated tilt. Now,inasmuch as rotation is occurring in the direction of the arrow 25), thegroove will be proccefiir g clockwise down the, incline to the pointmarked 90. As this occurs, the corresponding ball 25, which has beenheld by centrifugal force out on the disc radius r comfis progressivelyunder the influ nce of gravity which causes it to roll clockwise againstthe .retra t 0f n rifu al force t e po itio a e r tat n, pro e d to thepoint mark d 8 th influ nc o ravity. to ther with the constantcentrifugal force tends to bring the ball back to the center of thegroove on the adi s of t di a 26b, Rot t on p oceedin to the pointmarked 27.02 the force of gravity again opposes the centrifugal force,causing the b l t mor t F n e he sc h ma e om te can rn to the po nrnarlred 0, gravity, acting with the centrifugal force, restores theball to the center of the groove, at 26. Considering all four balls intheir four respective grooves, it is evident that a shift in center ofgravity of the disc l9 takes place, which is towards 180 when tilted asin Fig. 3.

It will be observed that due to the combined rotation and tilt of disc58 durin a tilt of the scope the balls L-fid oscillate; periodin therespective grooves 2 le it, theorgane ization thus constituting adynamic harmonic system. It will also beobserved thatthenatural period;of oscillation of the balls. is the same the period of rotation of discit! regardless of the rate of rotation during a tilt of the disc andthat the phase of ball oscillation is approximately out of phase withthe disturbance cause. Consequently, the system of this invention actsto rapidly neutralize any tilt of the gyroscopev G, by applying arighting couple in a vertical plane 90 to the tilt plane. Thus, underany condition of gyroscope tilt'the balls immediately assume acorresponding but complex pattern of oscillation in their correspondinggrooves to exert the proper righting couple without overshooting,becausc of the short radius R of their oscillating limit, i. e., thegrooves, combined with the action of centrifugal force due to discrotation. Hence, although adjacent balls move in opposite directionsduring a tilt, as depicted in Fig. 3., the net effect is to unbalancethe gyroscope G 90 to the precession or tilt, thereby causing the tiltto disappear at once. In most instances, two or more symmetricallyarranged grooves and balls will be used, but in some cases one grooveand ball will serve the purpose.

Although a preferred embodiment of themventicn has been illustrated anddescribed herein, it is to be understood that the invention is notlimited thereby, but is susceptible of changes in form and detail withinthe scope of the appended claims.

I c a m:

1. An harmonic stabilizing system for vertical axis gyroscopes,comprising at least one eccene tric guide displaced from and lying in aplane normal to the gyroscope axis with its center portion displacedfurther from said axis than its end portions, means for uniformlyrotating said guide bodily about said axis in said plane, and a 33ormallrposi oned b ce ri al Q IQE n the center portion of said guide,said guide having substantially parallel walls defining a paththerebetween of suficient width to accommodate said mass and to permitsynchronous oscillation of said mass to either side of the guide alongsaid path inresponse tothe centrifugal force and gravity during atilt ofsaid gyroscope to create an. erecting couple in the righting plane ofsaid gyroscope.

2. An harmonic stabilizing system for vertical axis gyroscopes,comprising at least one curved guide displaced from and lying in a planenormal tothe gyroscope axis and whose center of curv-a-. ture iseccentric to said axis with its center portion displaced further fromsaid axis than its end portions, means for uniformly rotating said guidebodily about said axis in said plane, and a mass normally positioned bycentrifugal force in the center portion of said guide, said guide havingsubstantially parallel walls defining a paththere between of suFlcientwidth to. accommodate said and to permit synchronous oscillation of massto either-side of the, guide along said path in response to thecentrifugal force and gravity during a tilt of said gyroscope. to createan. erecting couple in the righting plane'of said gyroscope.

3'. An harmonic stabilizing systemfor vertical axis gyroscopes,comprising. at least one eccentric guide displaced from and lying in aplane normal tothe gyroscope axis withv its center portion displaced:further from, said axis than its end porti n, m an for uniformly r atinaid guid oclflv a sa axisi sa r n l a a ball normally positioned bycentrifugal force in :the nte or ion sa d g ide. said gu d hav ngsubstantially parallel walls defining a path thercbetween of sufficientwidth to accommodate said ball and to permit synchronous oscillation ofsaid ball to either side of the guide along said path in response to thecentrifugal force and gravity during a tilt of said gyroscope to createan erecting couple in the righting plane of said gyroscope.

l. An harmonic stabilizing system for vertical axis gyroscopes,comprising at least two curved guides symmetrically disposed about andin a plane normal to the gyroscope axis and whose centers of curvaturelie in said plane between the corresponding guide and said axis, meansfor uniformly rotating said guides bodily about said axis in said plane,and a ball normally positioned by centrifugal force in the centerportion of each of said guides, each of said guides having substantiallyparallel walls defining a path therebetween of sufficient width toaccommodate a ball and to permit synchronous oscillation of the ball toeither side of the guide along said path in response to the centrifugalforce and gravity during a tilt of said gyroscope to create an erectingcouple in the righting plane of said gyroscope.

5. An harmonic stabilizing system for vertical axis gyroscopes,comprising a member carried by said gyroscope and rotated about and in aplane normal to the gyroscope axis, guides in said member having acurvature in a plane normal to and symmetrically arranged about saidaxis, the centers of curvature of said guides lying in said planebetween the corresponding guide and said axis, whereby the ends of saidguides curve inwardly toward said axis, and a mass in each of saidguides and urged to the point therein most remote from said axis by thecentrifugal force of said rotation, each of said guides havingsubstantially parallel walls defining a path therebetween of suflicientwidth to accommodate the mass contained therein and to permitsynchronous oscillation of said mass to either side of the guide alongsaid path in response to gravity during a tilt of said gyroscope toexert an erecting couple thereon in a vertical plane substantially fromthe vertical plane of said tilt.

6. An harmonic stabilizing system for vertical axis gyroscopes,comprising a member carried by said gyroscope and rotated about and in aplane normal to the gyroscope axis, cavities in said member having acurvature in a plane normal to and symmetrically arranged about saidaxis, the centers of curvature of said cavities lying in said planebetween the corresponding cavity and said axis, whereby the curvature ofeach cavity is less than the curvature of the periphery of said member,and a ball in each of said cavities and urged to the point therein mostremote from said axis by the centrifugal force of said rotation, each ofsaid cavities having substantially parallel walls defining a paththerebetween of suflicient width to accommodate a ball and to permitsynchronous oscillation of the ball to either side of the guide alongsaid path in response to gravity during a tilt of said gyroscope toexert an erecting couple thereon in a vertical plane substantially 90from the vertical plane of said tilt.

CHARLES T. DAVENPORT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

